This invention relates to moisture absorbing products. More specifically, this invention relates to moisture absorbing products, which are particularly useful for hanging within shipping containers, such as railroad cars.
Moisture absorbing products which absorb water vapor, liquid water and the like are known in the art. Generally these products are comprised of a water and/or water vapor permeable packaging material formed from fibrous or film products securely sealed at the edges of the packaging material. The packaging material encapsulates a water absorbing material, such as silica gel. The volume of water or water vapor absorbed by these moisture absorbing products is generally determined by the water absorbing capacity of the absorbing material contained within the packaging material.
One type of moisture absorbing product absorbs both water vapor and liquid water by permitting both to pass through the packaging material to contact the water absorbing material. In some circumstances the packaging material for this type of product dissolves when contacted with liquid water to permit the water absorbing material contained therein to contact directly the liquid water.
Another type of moisture absorbing product preferentially absorbs water vapor. The packaging material for this type of moisture absorbing product is chosen to prevent liquid water, which is absorbed within the product by the water absorbing material in the form of water vapor, from being released from the product in the form of liquid water.
There are many common water absorbing materials used with these products. Among the most common are silica gel, calcium sulfate, calcium fluoride, activated charcoal, molecular sieves, lithium chloride, calcium chloride and other such materials. A list of some of these materials is contained, for example, in Kirk-Othmer, Encyclopedia of Chemical Dictionary, 2nd Edition, Vol. 7, pages 378-398. In addition to the use of a single water absorbing material, such as silica gel, mixtures of different water absorbing materials have also been used.
A common method that is used to ship consumer and commercial products is by use of a shipping container such as a railcar. These shipping containers can hold a significant quantity of consumer or commercial products. However, the atmosphere of these containers sometimes also contains high humidity. To control the level of humidity within these containers, it is often necessary to utilize moisture absorbing products placed within these containers. Further, because of the structure of these containers, there is often a limited availability of space for placement of such moisture absorbing products within the containers.
It is often important that the relative humidity within these containers be maintained within a relatively narrow range during the entire shipping process. By controlling the relative humidity, thereby controlling the dew point, condensation of moisture within the container is prevented, thereby limiting the formation of liquid water.
When moisture absorbing products are placed within such containers, they are designed to absorb water vapor from the surrounding atmosphere. After a predetermined quantity of water vapor is absorbed, the water absorbing products may reach a saturation point and begin to give off liquid water or a liquid water-containing solution, depending on the water absorbing capacity of the moisture absorbing product that is used. It is important that any liquid water or liquid water-containing solution which is generated by these water absorbing products not be released from the water absorbing product into the container as such liquid water or solution can cause damage both to the commercial products being shipped and to the container itself.
Therefore, it is one object of a preferred embodiment of the invention to prepare a new and improved moisture absorbing product which is particularly useful for absorbing moisture that may be present within commercial products being shipped within a container, and within the atmosphere of the container itself during the shipping process without giving off liquid water.
This object and other objects and features of the present inventions will become apparent to those skilled in the art from a consideration of the following detailed description and drawings. The description, along with the accompanying drawings, provides a selected example of the construction of products to illustrate the invention, but does not limit the scope and coverage of the invention that is disclosed herein.